User:SH4ever/HLG

HLG refers to either a transfer function (Hybrid log–gamma) or to an HDR format (HLG10).

The HLG10 format, commonly simply named HLG, is an HDR format that use the HLG transfer function, BT.2020 color primaries and a bitdepth of 10-bit. HLG10 is backward compatible with SDR UHDTV, however it's not intended to be backward compatible with traditionnal SDR displays that can't interpret the BT.2020 colorimetry.

The Hybrid log–gamma (HLG) transfer function is a transfer function jointly developed by the BBC and NHK for high dynamic range (HDR) display. It's backward compatible with the transfer function of SDR (the gamma curve). It was approved as ARIB STD-B67 by the Association of Radio Industries and Businesses (ARIB). It is also defined in ATSC 3.0, Digital Video Broadcasting (DVB) UHD-1 Phase 2, and International Telecommunication Union (ITU) Rec. 2100.

Both HLG transfer function and the HLG format are royalty-free. They are supported by HDMI 2.0b, HEVC, VP9, and H.264/MPEG-4 AVC,   and are used by video services such as BBC iPlayer, DirecTV, Freeview Play, and YouTube. The partial backward compatibility allows them to be used with existing transmission standards, reducing complexity and cost for both equipment manufacturers and content distributors when the receiver is compatible with the BT.2020 colour container.

The HLG transfer function is backward compatible with SDR video  but the Rec. 2020 color space is not compatible with SDR color space (Rec.709).

Hybrid log–gamma (HLG) is a backwards-compatible high dynamic range (HDR) standard that was jointly developed by the BBC and NHK. It provides the ability to encode a wide dynamic range, while still being compatible with the existing transmission standards in the standard dynamic range (SDR) region. This makes HLG compatible with SDR displays, reducing complexity and cost for both equipment manufacturers and content distributors.